Sonic agitating method and apparatus



1967 N. G. BRANSON SONIC AGITATING METHOD AND APPARATUS Filed April 6, 1965 E m E mu LO V FIG.

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NORMAN G. BRANSON INVENTOR Em. L fizz United States Patent Ofiice 3,351,539 Patented Nov. 7, 1967 3,351,539 SONIC AGITATIN G METHOD AND APPARATUS Norman G. Bransou, Stamford, Conn., assignor, by mesne assignments, to Branson Instruments, Incorporated, Stamford, Conn., a corporation of Delaware Filed Apr. 6, 1965, Ser. No. 446,008 Claims. (Cl. 204-14) This invention refers generally to an agitating device for imparting vibratory energy to a liquid. More specifically, this invention has reference to a device which provides for a cyclically cavitated liquid, particularly an electrolytic plating solution.

The use of sonic or ultrasonic energy for agitating and cavitating an electrolytic plating solution is well known. Unfortunately, the results hoped for have not materialized and the improvement in electroplating due to the sonic or ultrasonic energy imparted by the present methods to the electrolytic solution must be considered marginal.

An analysis of this problem appears to reveal that the major deficiency of the known arrangement resides in the fact that the ultrasonic energy most commonly provided sets up standing waves which may even interfere with a uniform plating deposit. Hence, substantially improved results are achieved by applying the sonic or ultrasonic energy to a plating solution in pulse energy form which has the characteristics of a damped oscillation and is adapted to perform a two-fold function, namely to remove any particle of foreign matter which remains on the article to be plated and, secondly, to agitate the electrolyte so as to obtain uniform distribution thereof and intimate contact with the article to be plated. The use of such pulsed energy avoids the common shadow pattern associated with a standing wave pattern.

In application for U .8. Letters Patent Ser. No. 441,609 filed Mar. 22, 1965 and now Patent No. 3,318,578, entitled, Cleaning Apparatus, I have disclosed a liquid submersible enclosure which contains one or more electromechanical transducers for converting electrical energy to mechanical vibration in the sonic or ultrasonic frequency range as well as an electrical circuit for accepting electrical energy at line frequency and line voltage and converting such energy to high frequency for driving the transducers. The present invention makes use of a submersible enclosure of this type but includes, moreover, special circuit means and other provisions for making the unit especially suited for electroplating installations.

One of the principal objects of this invention is, therefore, the provision of a new and improved sonic energy generating unit for electroplating installations.

Another object of this invention is the provision of a submersible enclosure containing one or more transducers and electrical circuits for cyclically imparting vibrations to an electrolyte, the vibrations being of such nature as to set up a non-standing wave pattern.

Another object of this invention is the provision of a submersible sealed unit which, when immersed in an electrolytic plating solution and suitably energized with electric energy, cyclically pulses such solution with sonic energy.

A further object of this invention is the provision of a unit for immersion in an electrolytic plating apparatus to provide improved electroplating results.

Further and still other objects of this invention will be more clearly apparent by reference to the following description when taken in conjunction with the accompanying figures, in which:

FIGURE 1 is a perspective schematic view of the general arrangement of the invention;

FIGURE 2 is a sectional view of the sonic agitating device;

FIGURE 3 is a schematic electrical circuit diagram of a typical circuit used for producing cyclically a damped oscillation, and

FIGURE 4 is a typical wave shape caused by the circuit per FIGURE 3 and appearing across the transducer.

Referring now to the figures and FIGURE 1 in particular, there is shown a tank It? which is adapted to be filled with a suitable electrolytic plating solution 18. Two electrodes, numerals 12 and 14, are connected to a D-C power supply 16. This arrangement is illustrative of a typical electroplating apparatus, the precise arrangement of which is well known to those skilled in the art and need not be described further. The tank 10 is provided also with a submersible enclosure 20 which is connected to line voltage and line frequency 11 by means of a power cord 22. The enclosure 2% contains one or more electromechanical transducers 24 and an electrical circuit for energizing the transducers, thereby providing agitation for the solution 18.

The construction of the enclosure 20 will be apparent more clearly by reference to FIGURE 2 and, in general, follows the teachings of the aforementioned application for Letters Patent. The enclosure 20 contains a metallic shelf 28 which supports substantially all of the heat dissipating electrical circuit components, such as a rectifier 42, a power transistor 52, and various other circuit components shown in greater detail in FIGURE 3. Other components are mounted underneath the shelf. This circuit accepts line voltage at line frequency from a power cable 22 which seals with the enclosure by the use of a liquid tight electrical connector 23. The inside of the front wall 26 of the enclosure 20 is provided with a plurality of electromechanical transducers which are electrically connected to the circuit and mechanically bonded to the enclosure wall by an epoxy resin. The transducers are of the electrostrictive kind and, in a typical case, may comprise the structure disclosed in Patent No. 3,066,232, issued to Norman G. Branson, dated Nov. 27, 1962, entitled Ultrasonic Transducer. It will be apparent that other types of transducers, for instance magnetostrictive transducers, may be employed without deviating from the principle of this invention. The heat dissipated by the electrical circuit components mounted upon the shelf 28 is transferred from the shelf to the enclosure 20 by conduction, but it shall be understood that the other heat transfer means described in the aforesaid co-pending application for US. Letters Patent may be used. In order to protect the enclosure 20 from chemical reaction with the electrolyte, it may be made of chemically resistive material, such as titanium or Hasteloy, or the outside of the enclosure 20 may be protected by a suitable coating 39 of polyvinyl chloride, Teflon, Kel-F or the like.

The typical electrical circuit disposed inside the enclosure 20 and adapted to receive electrical energy directly from the power line and providing high frequency electrical energy to the transducers 24 is shown in FIGURE 3. The line power is received at a connector 21 and supplied via a conductor 22 to a bridge rectifier 42, the output of which is coupled to a filter capacitor 44 and an inductance 46. The direct current output. from this rectifier-filter combination charges a capacitor 48. The capacitor, at periodic time intervals, discharges its stored energy through a silicon controlled rectifier 52, thereby causing current to flow through the primary winding of the transformer 50. The secondary winding of the transformer 50 is connected across the parallel combination of a capacitor 54 and electromechanical transducers 24. The transducers 24, together with the capacitor 54 and the inductive secondary transformer winding, constitute an oscillatory circuit. As the voltage produced by the secondary transformer winding is applied to the transducers 24, sonic energy is imparted to the plating solution 18. The

frequency of discharge of the capacitor 48 is controlled by an adjustable resistor 60 and a series connected capacitor 62, which combination controls the conduction of a Shockley transistor diode 58, the latter being connected in series with a limiting resistor 66 to the control electrode of the silicon controlled rectifier 52. Resistor 64 serves to dissipate energy from the capacitor 62.

The circuit as shown in FIGURE 3, therefore, charges capacitor 48 with a direct current potential and periodically discharges the capacitor by establishing conduction through the rectifier 52. The discharge current through the primary winding of the transformer 50 causes a shock excitation in the secondary transformer winding and the associated circuit. The voltage applied to the electrostrictive transducers 24 has the characteristic of a damped oscillation, such as is shown by the curve 70 in FIGURE 4. This oscillation, in a typical case, is produced at a pulse repetition rate of 200 cycles per second and has a fundamental frequency of 40 kilocycles per second. It will be apparent, however, that other pulse repetition rates and different frequencies may be employed without deviating from the scope of this invention.

It will be seen, therefore, that the submersible enclosure 20 contains all of the elements and circuits for cyclically applying acoustic energy to the electrolyte, and that this energy is applied cyclically in a manner so as to avoid standing wave patterns. The acoustic energy generally is sufiiciently powerful to cause cavitation of the electrolyte for displacing small foreign particles which may be present on the article to be plated and, at the same time, to agitate the electrolyte to the degree necessary for providing uniform concentration thereof. In view of the clamped oscillation type cavitation applied to the electrolyte, the shortcomings experienced heretofore when using continuous wave high frequency oscillators or other circuits having a harmonic pattern are eliminated and improved plating results are achieved.

While there has been described and illustrated a certain preferred embodiment of the present invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without deviating from the principle and intent of the present invention which shall be limited only by the scope of the appended claims.

What is claimed is:

1. In an electrolytic plating apparatus which includes the combination of a tank adapted to contain an electrolyte, a set of electrodes, means for impressing an electrolyzing current across said electrodes, and means for agitating said electrolyte ultrasonically, the improvement wherein said agitating means comprises a sealed, liquid immersible enclosure containing:

(a) at least one electromechanical transducer coupled to one wall of said enclosure for providing thereto vibratory energy;

(b) an electrical circuit for receiving low frequency line voltage electrical energy and converting it to pulsed high frequency energy coupled to said transducer for causing, when energized, said transducer to provide periodically vibratory energy having a damped oscillation wave characteristic;

(c) electrical circuit connecting means disposed on said enclosure for providing low frequency line voltage electrical energy from without said enclosure to said electrical circuit,

whereby when the exterior of said enclosure is immersed in the electrolyte and said circuit is energized, said transducer cyclically cavitates said electrolyte in a non-standing wave pattern.

2. In an electrolytic plating apparatus as set forth in claim 1 wherein said electrical circuit includes capacitor charge and discharge means.

3. In an electrolytic plating apparatus as set forth in claim 1 wherein the outside of said enclosure is provided with a coating which is substantially non-reactive with the electrolyte.

4. In an electrolytic plating apparatus which includes the combination of a tank adapted to contain an electrolyte, a set of electrodes for contact with said electrolyte, means for impressing an electrolyzing current across said electrodes, and means for agitating said electrolyte ultrasonically, the improvement wherein said agitating means comprises a sealed, liquid submersible enclosure containmg:

(a) a plurality of sonic energy transducers mechanically coupled to said enclosure for providing thereto vibrotory energy;

(b) an electrical circuit for receiving low frequency line voltage electrical energy and converting it to pulsed high frequency energy coupled to said transducers for causing, when energized, said transducers to provide pulses of energy in the ultrasonic frequency range, which energy has the characteristic of damped oscillations;

(c) electrical circuit connecting means disposed on said enclosure for providing low frequency line voltage electrical energy from without said enclosure to said electrical circuit within said enclosure,

whereby when the exterior of said enclosure is inserted in the electrolyte,'said transducers cavitate the electrolyte in a non-standing wave pattern.

5. A method of electrolytic plating comprising the provision of an electrolytic plating solution, and cyclically imparting to said solution sonic energy pulses having a frequency in the ultrasonic frequency range and having the characteristic of a damped oscillation to provide a non-standing wave pattern in said solution.

References Cited UNITED STATES PATENTS 2,702,260 2/1955 Massa 204-14 2,744,860 5/1956 Rines 204222 2,760,501 8/1956 Gander 1341 3,180,626 4/1965 Mettler 2591 ROBERT K. MIHALEK, Primary Examiner.

T. TUFARIELLO, Assistant Examiner. 

5. A METHOD OF ELECTROLYTIC PLATING COMPRISING THE PROVISION OF AN ELECTROLYTIC PLATING SOLUTION, AND CYCLICALLY IMPARTING TO SAID SOLUTION SONIC ENERGY PULSES HAVING A FREQUENCY IN THE ULTRASONIC FREQUENCE RANGE AND HAVING 